Some conventional vehicle seat reclining devices include a first rotating member, a second rotating member arranged coaxially with the first rotating member, a locking member that limits relative rotation between the first and second rotating members. The seat reclining device disclosed in Patent Document 1 further includes a first memory member and a second memory member. The first memory member engages with the outer surface of the first rotating member through friction. The second memory member engages with the first memory member at a predetermined relative rotation position to restrict the first memory member from rotating relative to the second rotating member. In the above described configuration, when the seat back is folded forward to execute a walk-in access enabling action for facilitating entry into and exit from the rear seat, the locking member is either locked or unlocked in conjunction with engaging/disengaging action of the second memory member with the first memory member. This allows the seat back, which has been folded forward, to be returned to the inclined position at which the seat back was located before the forward folding operation.
Many of the above seat reclining devices have an operation handle on the side of the seat. The operation handle is manipulated to cause the locking member to cancel the constraint between the first and second rotating members, so that the tilt angle of the seat back can be adjusted. At a normal reclining operation, the seat reclining device disclosed in Patent Document 1 causes the second memory member to engage with the first memory member to restrict the first memory member from rotating relative to the second rotating member. The first rotating member is allowed to rotate relative to the second rotating member by acting against the frictional engagement force between the first rotating member and the first memory member.
In contrast, at the time of walk-in access enabling action, the locking member is unlocked in conjunction with separation of the second memory member from the first memory member. That is, when the second memory member is separated from the first memory member, the first memory member and the first rotating member rotate integrally due to the frictional engagement force. Then, when the forward folded seat back is raised, the second memory member is engaged with the first memory member at a predetermined relative rotation position, so that the seat back is returned to the inclined position at which the seat back was located before the forward folding operation.
In this conventional example, a memory ring 91 is employed as the first memory member. As shown in FIG. 20, the memory ring 91 has an engagement slot 90 at a predetermined position in the circumferential direction. Further, a substantially columnar memory pin 92 is employed as the second memory member. The memory pin 92 enters and exits (engages with and disengages from) the engagement slot 90 in the memory ring 91, while locking and unlocking the locking member.
That is, when the memory ring 91 rotates relative to the second rotating member, the memory pin 92, which has exited the engagement slot 90, slides on an outer circumferential surface 91s of the memory ring 91. This restricts an engaging action of the memory pin 92, which is accompanied by the locking action of the locking member. Also, returning the memory ring 91 to the predetermined relative rotation position, at which the memory pin 92 is capable of entering the engagement slot 90, permits the engaging action of the memory pin 92, which is accompanied by the locking action of the locking member.
However, in the above described conventional configuration, after relatively moving on the outer circumferential surface 91s of the memory ring 91, the memory pin 92 enters the engagement slot 90 with the circumferential portion apparently sliding on the boundary between the engagement slot 90 and the outer circumferential surface 91s, which is a sliding surface. That is, the engaging action of the memory pin 92, which is accompanied by the locking action of the locking member, starts when the memory pin 92 has not completely reached the entry position with respect to the engagement slot 90. Thus, the locking member is locked while the first and second rotating members are still moving relative to each other. This applies load on the locking member and the rotating members, which may produce noises and lower the durability.